This application is filed contemporaneously with three other U.S. patent applications, entitled respectively "Dual Chamber Culture Bottle with Rotating Inlet Valve Assembly," application Ser. No. 08/475,380; "Dual Chamber Blood Culture Bottle with Break Seal," application Ser. No. 08/477,656; and "Dual Chamber Blood Culture Bottle with Syringe Capture and Piston Assembly," application Ser. No. 08/477,655; each by the same inventors as the present application, and each assigned to the owner of the present application.
The present invention relates generally to blood culture bottles and more particularly to a multi-chambered blood culture apparatus that may simultaneously perform a plurality of different tests on a sample of blood. Blood culture tests are typically performed to diagnose certain types of systemic infections present in the blood of a patient. In such a test, a sample of blood is first extracted from a patient, typically with a hypodermic syringe. The blood sample is then combined with a sterile nutrient growth medium and incubated under defined conditions for a period of time ranging from hours to weeks in order to encourage the growth of any blood-borne pathogens that may be present. Because human blood is normally sterile, and assuming that proper aseptic technique is practiced in the collection of the specimen and the performance of the test, no microbial growth will be observed in the absence of infection. If an infection is present, however, microbial growth will occur and may be detected by any number of well known methods, including light scattering, optical absorbance, fluorescence and pressure change.
The selection of the growth medium and incubation conditions employed determines the types of microorganisms that are most likely to grow during a given test. In most cases of suspected infection, the type of infecting microorganism is not known. In such cases, it is common practice to prepare two blood specimens from the given patient and to perform separate blood culture tests on the two specimens. Usually, one of the specimens is tested in a blood culture bottle containing an aerobic growth environment, while the other specimen is tested in a blood culture bottle containing an anaerobic growth environment. This arrangement may enable a detection of microorganisms in the blood that thrive in an oxygen-rich environment, or, alternatively, microorganisms in the blood that thrive in an oxygen-poor environment. It is also common practice to repeat each of these tests so as to improve the probability of detecting a blood-borne infection. In addition, blood culture tests using varied growth media and incubation conditions may be employed in order to refine the initial diagnosis.
The performance of each blood culture test bears inherent costs. For instance, each blood culture test requires a specimen to be collected and transported in a suitable blood culture bottle to a laboratory. Growth media and ancillary materials must be obtained. The blood culture bottles must be prepared, and the specimens must be inoculated into the blood culture bottles. A suitable incubator must be provided, and the bottles containing specimens must be incubated under prescribed conditions for each given test. Microorganism growth must then be monitored during incubation. Finally, upon completion of the test, any contaminated materials that were generated, including the specimen collection and handling devices and the blood culture bottle, must be properly sterilized and disposed of. Each of these operations contributes to the cost of blood culture testing.
In addition, inherent risks are associated with every blood culture test. Each time an additional test is performed, the probability increases that a test bottle will be mislabeled, misdirected or improperly prepared, or that the test itself will be improperly performed or flawed. At best, such errors would necessitate repeating the test at an additional cost; at worst, such errors can result in an incorrect diagnosis for the patient. Risks are also present as a result of the frequent use of hypodermic syringes to collect blood specimens and inoculate the specimens into the blood culture bottles. The performance of each additional test increases the potential for accidental needle sticks, which, in the presence of any infectious microorganisms, may seriously infect the testing technician. In some cases, instead of using hypodermic syringes to inject the blood specimen into a sealed blood culture bottle, the blood specimen is pipetted into an open blood culture bottle and the bottle is then sealed. With this procedure, however, an increased risk exists that the bottle contents will inadvertently become contaminated and will yield erroneous diagnostic results.
In addition, blood culture bottles are traditionally made of glass and are therefore prone to break before, during and after use. While breakage before use merely increases costs, breakage during or after use presents a serious risk of infecting the testing technician. Additionally, in order to minimize the risk of contamination, blood culture bottles are usually sealed after being inoculated with a blood specimen. A sealed blood culture bottle is also required if a pressure sensor is used to detect microbial growth. However, certain specimens may generate enough pressure within the sealed bottle that the bottle may burst during incubation or the contents may spurt from the bottle when the seal is broken after testing. Both of these situations present an increased risk of infecting the technician with every additional blood culture test performed.